Pretreatment of Rapeseed Meal Increases Its Recalcitrant Fiber Fermentation and Alters the Microbial Community in an in vitro Model of Swine Large Intestine.

Cheng Long,Koen Venema

doi:10.3389/fmicb.2020.588264

Abstract

The aim of current study was to investigate in an in vitro study how enzymatic and chemical pretreated rapeseed meal (RSM) influences the fiber fermentation and microbial community in the swine large intestine. RSM was processed enzymatically by a cellulase (CELL), two pectinases (PECT), or chemically by an alkaline (ALK) treatment. 16S rRNA gene sequencing data was performed to evaluate changes in the gut microbiota composition, whereas short-chain fatty acid (SCFA) production (ion-chromatography) and non-starch polysaccharides (NSP) composition (using monoclonal antibodies; mAbs) were used to assess fiber degradation. The results showed that ALK, CELL, PECT1, and PECT2 changed microbial community composition, increased the predicted abundance of microbial fiber-degrading enzymes and pathways, and increased acetic acid, propionic acid, butyric acid, and total SCFA production. The increased microbial genera positively correlated with SCFA production. Monoclonal antibody analyses showed that the cell wall polysaccharide structures of RSM shifted after ALK, CELL, PECT1, and PECT2 treatment. The degradation of NSP during the fermentation period was dynamic, and not continuous based on the epitope recognition by mAbs. This study provides the first detailed analysis of changes in the swine intestinal microbiota due to RSM modified by ALK, CELL, PECT1, and PECT2, which altered the microbial community structure, shifted the predicted functional metagenomic profile and subsequently increased total SCFA production. Our findings that ALK, CELL, PECT1, and PECT2 increased fiber degradability in RSM could help guide feed additive strategies to improve efficiency and productivity in swine industry. The current study gave insight into how enzymatic treatment of feed can alter microbial communities, which provides good opportunity to develop novel carbohydrase treatments, particularly in swine feed.

Highlights

Rapeseed meal (RSM), a by-product of rapeseed oil production, is a suitable protein source for swine feed and a potentially energy source
ALK strongly increased binding of non-fucosylated XG Monoclonal antibodies (mAbs), while CELL, Pectinex Ultra SP (PECT1), and Multifect Pectinase (PECT2) led to disappearance of those compared to CON, regardless of _A and _B treatment
ALK, PECT1, and PECT2 increased binding of mAbs directed against the arabinogalactan side chains of RGI (RG-I/AG)

Summary

Introduction

Rapeseed meal (RSM), a by-product of rapeseed oil production, is a suitable protein source for swine feed and a potentially energy source. The primary cell walls of RSM consist of pectin and xyloglucan and its cellulose microfibrils are interlinked with xyloglucan via hydrogen bonds forming a stiff network (Carpita and Gibeaut, 1993). Pectins, consisting of homogalacturonan, rhamnogalacturonan, xylogalacturonan, arabinogalactan and arabinan, are the major polysaccharides present in the dehulled rapeseed meal (Eriksson et al, 1997). In the secondary cell wall of RSM, the main carbohydrates are 4-O-methyglucuronoxylan, xyloglucan, and cellulose. A drawback of using RSM in animal feed is that the complex cell wall polysaccharides cannot be utilized by endogenous enzymes from monogastric animals (e.g., pigs), and can only partly be fermented by the microbial community in the gastrointestinal tract (GIT) of the pig

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